Abrasives



hereinafter.

, Patented May 25, 1943 UNITED "STATES. PATENT OFFICE? l Y ABRASIVESLoring Goes, Jn, Brookfleld, Mass., assignmto Norton Company, Wor tionof Massachusetts cester, Mass., a corpora- No Drawing. Application July23, 1942,

' Serial No. 452,088

I 8 Claims. (cus -29s) ble of splitting of! hydrogen halide at elevatedtemperatures and/or of alkylating an aromatic grinding wheel or othersolid abrasive article which, in various embodiments, may be substitutedfor abrasive articles bonded with shellac,

rubber or phenol-formaldehyde, and which will remove a greater amount ofmetal for a given wheel wear. V o r Another object of the invention isto provide an ingredient for assisting the conversion of an aromaticamine-aldehyde resin, particularly'aniline-formaldehyde, to theinfusible condition. Another object of the invention is to provide .amixing plasticizer for abrasive: grains having properties superior tofurfural for the manufacture of the type of abrasive articles indicated.Another object of the invention is to provide a mixing plasticizer whichdoes not react to form water. v I

Another obj ect of the invention is to provide a wetting agent forcarrying out the dry granular mix method in the manufacture of the typeof abrasive articles indicated of superior quality.

Another object is to avoid or prevent swelling of the abrasive article;to permit coldpressing and curing without pressure, and to avoid theformation of any water during the cure. Other objects will be in partobvious or in part pointed out The ln'ventionaccordingly consists in thefea-- tures of construction, combinations of elements, arrangements ofparts, and in the several steps and relation and order of each of saidsteps to one or more of the-others thereof, all as will beillustratively described herein, and thescope of the application ofwhich willbe indicated in the following claims.

I provide a quantity of a; primary aromatic amine, such as aniline,ortho, meta or para toluitityof formaldehyde. I may optionally provide aquantity of one or more organic compounds containing afhalogen selectedfrom the group consisting-of chlorine, bromine and iodine and capaaminepolymer, providing'cross'links connecting amine groups of the chains.The aromaticamine which I now prefer to use is aniline. Aniline NH: I

or one of the other aromatic amines mentioned, or mixtures of two ormore of such amines, is reacted; with formaldehyde HCHO in the presenceof a strong acid to produce a long chainppolymer which, when an excessof formaldehyde above the stoichiometric proportions is used, forexample,

20% excess, has adjacent chains connectedwith methylene CHa groups toform a tough, heat resistant, semi-thermoplastic resin; I may add someof the formaldehyde after the initial con- --ch.lorine, bromine oriodine substituted paraflin such as hexa'chlor ethane, tetra I 30. l, 2,diiodoethane, betabutylene densation, in the form of paraformaldehyde,or by the addition of hexa-methylene-tetramine.

As examples of the halogenated organic compound, I may'use any ofpolyvinyl chloride, poly vinylidene dichloride, rubber hydrochloride,chlorinated rubber, chlorinated polyisobutylene; any

hydrocarbon, chlor 'pentane, bromide, partly chlorinated eicosane, orany aliphatic halohydrin of notm'ore than six carbon .50 dine, ordiamino diphenyl methane; and a quanatoms,'such as any of the amylenechlorhydrins; propylene chlorhydrin; any of the butylene chlorhydrin's;ethylene chlorhydrin, ethylene bromhydrin, or glycerol alpha gammadichlorhydrin. Naturally enough, most of the examplesare chlorinatedcompounds because these are cheaper and more readily available than thefrominated or iodated compounds, but the latter two give efiectiveresults. The fluorinated compounds are rejected because they are toostable and will not alkylate the polymer. However, so far as the broadfeatures of this invention are concerned, and apart from the estershereinafter described,

the halogenated organic compound may be omitted altogether. I

Since the invention relates to grinding wheels and other solid abrasivcompositions and articles, I provide a quantity of abrasive grain. Anyabrasive grain may be used, for example, any of the varieties ofalumina, such as emery, corundum, dense regular fused alumina, porouswhite fused alumina; silicon carbide .and other hard carbides; quartz;glass:.garnet; or diamonds. Two

or more of these abrasives may be mixed, if desired.

Manufacturers usually prefer to use the dry granular mix method, withthe cold press and the oven to make organic bonded grinding wheelsbecause this combination of steps and features is the cheapest to carryout and, furthermore, generally gives uniform results. In the drygranular mix method the abrasive grains are placed in a mixing pan andare then wet with a suitable liquid; then powdered fusible resin isadded, mixing is done to coat each granule with some of the powder andto leave a minimum of loose powder, then a mold is charged with the "drygranular mix thus produced, the top plate is inserted, the mold is"closed by means of an hydraulic press, the mold is then stripped," thegreen wheel is taken to an oven and (at the same time as hundreds orthousands of, others of varying sizes, shapes and compositions) it iscured to make the final composition and, after truing or shaving," thefinal article, This method, in co'ntradistinction to the use of the hotpress with or without the autoclave and vice versa, has'the advantagethat ordinary ovens, in which -thousands of green" wheels can bestacked, are used; the hydraulic press is tied up by a given wheel forthirty seconds instead of thirty minutes, and the press need have noheated platens. This wetting of the abrasive grains by a liquid iscalled plasticizing. It is preferred that the wettant be a solvent forthe resin.

In the commercial manufacture of anilineformaldehyde resin bondedgrinding wheels and other solid abrasive products, only furfural hasbeen used as this plasticizer-wettant. (Other aromatic-amine-aldehydepolymers have not been used commercially for the manufacture of grindingwheels and other solid abrasive products so far as I an! aware.) Thefurfural cross links the polymer and, therefore, converts it to the"infusible condition. A stoichiometric quantity of aniline andformaldehyde condensed in the presence of a strong acid is believed toproduce a resin which is structurally represented thus:

H H H n O O O it 1'; Such a resin cross-linked'with furfural is believedto be represented thus:

My invention consists in the use of chloracetates of glycerolchlorhydrins as the wettantplasticizer for grinding wheels and othersolid abrasive articles made out of abrasive grains bonded witharomatic-amine-aldehyde resin with or without the use of otherhalogented compounds, with or without other fillers, and with or withoutthe use of other wettant-plasticizers; for example, a mixture of such achloracetate and furfural may be used to wet the abrasive grains, but atpresent I prefer to use a chloracetate or mixtures of chloracetatesalone.- I have found plasticizers and hardening agents for such resins.

A preferred and illustrative method of carrying out my invention may beas follows: I first prepare the chloracetate. For example, I may startwith glycerol (1') dichlorhydrin and glycerol afi dichlorhydrin, whichare, respectively, or may be written thus:

CHI-Cl CHr-Cl CHOH and CHC1 CHr-C]. CHI-OH Mixtures of the above formchloracetates when reacted with chloracetic acid; such chloracetatesare, respectively, or may be written thus:

These are esters and the mixture cross-links I believe, theaniline-formaldehyde, thus:-

n 1 Cl It will be noted that chlorine now appears in the amino group.When a grinding wheel according to the invention is'used to grind, theheat generated by grinding (which may'reach 500 C. or more and is ahigher heat than generated in most sanding operations with sandpaper orthe like) releases hydrogen chloride at the grinding line which appearsto have a pronounced effect upon the grinding operation, preventing orat least minimizing loading and assisting in the cutting action bymaking the metal chips more britt e.

Grinding wheels when made according to my invention achieve a number ofpractical advantages and the abrasive article may be made up withouthaving to tie up expensive hot-press equipment, and several methods,illustrations of which are later set forth, may be .used where it is notdesired to resort to hot-pressing. Thus the mix of resin (in powderform), abrasive grains, and chloracetate hardening agent, with orwithout other ingredients, fillers, or the like,

may be shaped in any. desired way cold, or at room temperature, andafter such playing may be put in an oven for heat treatment to cure theresin and effect the bonding together of the abrasive articles. Grindingwheels made according to my invention have or may be given, in general,cutting characteristics similar to those of hard-rubber bonded wheels,and thus may be used to perform grinding operations where such hardrubber-bonded wheels are preferred or more I ticles, lending itself,in'its intermediate stage, to

ready and facile molding, shaping or otherwise that such chloracetatescan'be'used as combined conforming it .to the desired configuration, and

lending itself thereafter to advantageous and,

economical heat treatment for curing or hardenins; .it is, however, tobeunderstood that, when the mix includes abrasive grains, many unique andhighly advantageous features of action and coaction, both in the processand in the abrasive article itself, are achieved. Thus, for example,

the esters bring to the cross-linking with the above-mentioned polymernot only hydrogen chloride, but also do so in a manner to free hydrogenchloride at the grinding line, under the heat effect produced duringgrinding. Moreover,

. the esters are good wettants for the abrasive grains and this is ofgreat advantage in that thereby it is made certain that each grainbecomes well coated by and with the particles of the powdered resin andthus there is good assur ance of achieving, during the curing, good andgroups.

uniform bonding of the abrasive grains, the

abrasive article having thereby substantial uniformity of strength andother characteristics throughout. The abrasive wheel can thus be madefreefrom localized mechanical weaknesses and its wear can be uniform.

There are hereinafter set forth several exby. the above-mentionedesters, of a resin or resinous article.

Also, insofar as I am aware, the above-mentioned esters are newcompositions 'of matter. These I may produce in any suitable way of whicthe following is illustrative, thus:-

1-30 grams of a commercial mixture of, :3 and a7 glycerol dichlorhydrinis mixed with 94 grams of chloracetic acid and the mixture is heated inan open flask at about 140 C. for about. 8 hours. The reaction mixtureis thenneutralized with sodium carbonate, washed with water and finallyheated at about 100 C. at reduced pressure, say, at 20 millimeters; forabout 3 hours The product is light yellow brownin color and has a slightpleasant odor. It is a good solvent for. aniline formaldehyde resin. i

Example I I I 525 grams of #46 grit Alundum abrasive grain is wet with20 cc. of the above-mentioned product which may be termed glycerolchlorhydrin chloracetate and thereto is added, with stir-- ring, 165grams ofa mixture, by volume, of 65% of aniline formaldehyde resin, 30%of cryolite, and 5% of soluble anhydrite, resulting in a dry granularmix. The latter is spread in a 6" mold, where a grinding wheel is to bemade, and pressed to the desired pore volume, in this instance, percent.The green ,wheel is then stripped. from the mold and cured in an oven.

iExample II 525" grams of- #80 grit Alundum abrasive grain is Wet withcc. of the above-mentioned ester and thereto is then added, withstirring, 165 grams of a mixture, by volume, of 65% of ananilineformaldehyde resin, of cryolite, and 5% of soluble anhydrite,resulting in a. dry granular .mix. .I

The latter is then worked on differential mixing rolls until formed intosubstantially a sheet and the sheet is then passed'through calendarrolls until the desired thickness is achieved, in this instance, 1?!-From the resultant sheet, a 12" disk is then cut and the resultant greenwheel is then heat-treated, preferably in v the manner described abovein Example I. I i

I It willbe understood that either of the esters or mixturesthereof maybe used, .following substantially the proportions of materialsillustrated in the foregoing two specific examples, and whether eitherester alone or the two in admixture are employed, it will be seen that,in the cross-linking with the above-mentioned polymer, the samerelationships appear, including the appearance of the hydrogen chlorideat the amino Wheels so made, running at a surface speed of 9500 fee,tper minute, when tested in grinding /4" cold rolled steel showed anareal wheel wear of 0.043 square inch per cut when running wet and 0.075square inch per cut when running dry.

A wheel; made according to Exam le I was tested as a portable snaggingwheel with good 'results; its resiliency was of such an order as togreatly facilitate, manual control of the positioning or movement of thewheel and the pressure of its applicationand gave the wheel a freecutting and smooth action." I

According tq certain prior practices, dimculties are encountered duringheat treatment or curing, due to the fact that swelling occurs; suchswelling usually results from the formation of water and is aggravatedby the conversion of water or possibly also of other-constituents intovapors, under the action of the heat treatment. But according, to myinvention such disadvan. tages and defects are successfully overcome andI find that, in practicing mylinvention, no such swelling occurs; thisis due to the fact that no water or other'liquid or vapors thereof, aswould i chlorhydrins of thetwo types; when reacted with Preferably, Iutilize an initial curing temperacause swelling, duringthe heattreatment 01 curing, are formed.

It will be understood that either of the abovementioned esters may beused alone or they may both be used in admixture; in any such case thecross-linking is as above set forth in connection with the mixture ofboth esters. In the illustrations above set forth, I have used mixturessimply because of the convenience in using commercially' availablealready-mixed glycerol dichloracetic acid as above described, a mixtureof the two chloracetates results. The illustrations above set forth are,therefore, not to be interpreted by way of limitation. 1

I make no claim herein to the resinous compositions or method ofmakingthe same or to the plastlcizer or hardening agent inasmuch as suchsubject matter is disclosed and claimed in my copending applicationSerial No. 452,089, filed of even date herewith.

' tion' and as'the; art herein described might be It will thus be seenthat; there has been provided by this invention, an article, acomposition and a method in which the various objects hereinabove setforth together with many thoroughly ractical advantages are successfullyachieved. As various possible embodiments might be made or themechanical features of the above inven varied invarious parts, allwithout departing derstood that all matter hereinbefore set forth is tobe interpreted as illustrative and not in a limiting sense.

I claim:

1. The method of making an abrasive wheel or other abrasive article,comprising wetting abra-. sive grains with a combined grain-wettant andresin-hardening agent that comprises a compound taken from the groupconsisting of the reaction product with chloracetic acid of glycerol a'ydichlorhydrin, the reaction product with chloracetic acid of glycerol415 dichlorhydrin and amixture thereof, admixing therewith amineformaldehyde resin to produce a dry granular the mold, and heat-treating"it at resin-curing temperature.

3. The method of making an abrasive wheel or other abrasive article,comprising wetting abrasive grains with a, combined grain-wettant andresin-hardening agent that comprises a compound taken from the groupconsisting of the reaction product with chloracetic acid of glycerolcz'y dichlorhydrin, the reaction product with chloracetic acid ofglycerol ,9 dichlorhydrin and a mixture thereof, admixing therewithamine formaldehyde resin to produce a dry granular mix, working the mixinto substantially sheet form and then giving it the desiredconfiguration of the abrasive article, and then heat-treating it atresin-curing temperature. 4. A grinding wheel or other abrasive articlecomprising abrasive grains bonded together by a bond that comprises thereaction product, under hcattreatment, of amine formaldehyde resin and ahardeningagentv comprising a compound selected from the group consistingof the-reaction product with chloracetic acid of glycerol adichlorhydrin, the reaction product with chloracetic acid of glycerol01B dichlorhydrin and a mixture thereof. a

5. A grinding wheelv or other abrasive article comprising abrasivegrains bonded together by a bond that comprises the reaction product,under I heat-treatment, of a resin-hardening agent comprising a compoundselected from the group consisting of the reaction product withchloracetic acid of glycerol a'y dichlorhydrin, the reaction productwith chloracetic acid of glycerol 043 di-' product with chloracetic acidof glycerol 043 dichlorhydrin and a mixture thereof.

'1. The method of making a grinding wheel or other abrasive bodycomprising making a mix comprising abrasive grain and resin and a,grainwetting and resin-hardening agent comprising a compound selectedfromthe group consisting of the reaction product with chloracetic acidof glycerol a'y dichlorhydrin, the reaction product with chloraceticacid of glycerol up dichlorhydrin and a mixture thereof, and shapin andcuring the mix.

8. The method of making a grinding wheel or other abrasive bodycomprising making a mix comprising abrasive grain and resin and agrainwetting and resin-hardening agent comprising a compound selectedfrom the group consisting of the reaction product with chloracetic acidof glycerol (17 dichlorhydrin, the reaction product with chloraceticacid of glycerol up dichlorhydrin and a mixture thereof, working the mixon mill rolls, then calenderin into. substantially sheet form to thedesired thickness, cutting out of the sheet form the desiredconfiguration of abrasive article, and then curing at resin-curingtemperature.

' LORING COES, JR.

